In the event of a ground fault or an inter-electrode short circuit fault (hereinafter referred to simply as a “fault”) in a DC line in self-excited DC power transmission using a self-turn-off semiconductor element, such as an IGBT (Insulated Gate Bipolar Transistor), the fault current continues increasing even after the converter for converting AC power to DC power (hereinafter referred to as an “AC-DC converter”) is no longer being controlled because current flows in from the AC side via a freewheeling diode for protecting the AC-DC converter elements. In Patent Literature 1, for example, when no DC circuit breaker is provided for interrupting this kind of fault current in a DC line, an interruption by the AC system's AC circuit breaker connected to the AC-DC converter eliminates the fault.
The elimination of a fault in a DC line by using a DC circuit breaker may be envisaged. For example, Patent Literature 2 proposes different interrupting methods using DC circuit breakers. In such a case, Patent Literature 3 discloses a method in which a current-limiting device is provided in a DC circuit in order to limit the fault current and thereby reduce the load on the DC circuit breaker.